In recent years, digital cameras (image sensing apparatuses) capable of photographing an image by a simple operation and converting the photographed image into digital image data have widely been used. To print an image photographed by this camera and use the print as a photograph, the photographed digital image data is temporarily input from the digital camera to a PC (computer), and undergoes image processing by the PC. Then, the processed data is output from the PC to a color printer, which prints the image data.
To the contrary, there have been developed color print systems capable of directly transferring digital image data from a digital camera to a color printer and printing the data without the mediacy of any PC, and so-called photo direct (PD) printers capable of directly mounting in a color printer a memory card which is mounted in a digital camera and stores a sensed image, and printing the photographed image stored in the memory card.
Especially when image data is to be directly transferred from a digital camera to a printer and printed, demands have arisen for the advent of a photo direct printer capable of coping with digital cameras of various vendors because the specifications and operating methods of digital cameras are different between vendors. Such photo direct printer receives and prints image data not only from the above-mentioned digital camera, but also from a cell phone, PDA, and other devices. Further, the printer has various functions. The printer and image supply device must confirm whether they can communicate with each other in accordance with a predetermined communication protocol.
In confirming whether communication complying with a new communication protocol is possible, a dedicated command or the like must be prepared. It is difficult to confirm whether communication is possible without changing an existing rule (PTP (Picture Transfer Protocol) or the like).